Ultra-faint [CII] emission in a redshift = 2 gravitationally-lensed metal-poor dwarf galaxy. (arXiv:2101.00841v2 [astro-ph.GA] UPDATED)

Ultra-faint [CII] emission in a redshift = 2 gravitationally-lensed metal-poor dwarf galaxy. (arXiv:2101.00841v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Rybak_M/0/1/0/all/0/1">M. Rybak</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cunha_E/0/1/0/all/0/1">E. da Cunha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Groves_B/0/1/0/all/0/1">B. Groves</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hodge_J/0/1/0/all/0/1">J. A. Hodge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aravena_M/0/1/0/all/0/1">M. Aravena</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maseda_M/0/1/0/all/0/1">M. Maseda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boogaard_L/0/1/0/all/0/1">L. Boogaard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berg_D/0/1/0/all/0/1">D. Berg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charlot_S/0/1/0/all/0/1">S. Charlot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Decarli_R/0/1/0/all/0/1">R. Decarli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Erb_D/0/1/0/all/0/1">D. K. Erb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nelson_E/0/1/0/all/0/1">E. Nelson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pacifici_C/0/1/0/all/0/1">C. Pacifici</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schmidt_K/0/1/0/all/0/1">K. B. Schmidt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walter_F/0/1/0/all/0/1">F. Walter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wel_A/0/1/0/all/0/1">A. van der Wel</a>

Extreme emission-line galaxies (EELGs) at redshift z=1-2 provide a unique
view of metal-poor, starburst sources that are the likely drivers of the cosmic
reionization at z$geq6$. However, the molecular gas reservoirs of EELGs – the
fuel for their intense star-formation – remain beyond the reach of current
facilities. We present ALMA [CII] and PdBI CO(2-1) observations of a z=1.8,
strongly lensed EELG SL2S 0217, a bright Lyman-$alpha$ emitter with a
metallicity 0.05 $Z_odot$. We obtain a tentative (3-4$sigma$) detection of
the [CII] line and set an upper limit on the [CII]/SFR ratio of
$leq1times10^6$ $L_odot$/($M_odot$ yr$^{-1}$), based on the synthesized
images and visibility-plane analysis. The CO(2-1) emission is not detected.
Photoionization modelling indicates that up to 80% of the [CII] emission
originates from neutral or molecular gas, although we can not rule out that the
gas is fully ionized. The very faint [CII] emission is in line with both nearby
metal-poor dwarfs and high-redshift Lyman-$alpha$ emitters, and predictions
from hydrodynamical simulations. However, the [CII] line is 30$times$ fainter
than predicted by the De Looze et al. [CII]-SFR relation for local dwarfs,
illustrating the danger of extrapolating locally-calibrated relations to
high-redshift, metal-poor galaxies.

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